OneDrive Differential sync all files (Dec 2019) and live/active PST files ?

Steel Contributor

Hi Everyone,

With the rollout of "Differential sync for all file types" in Dec 2019, does this mean that  PST files that are actively used by Outlook can now be stored in OneDrive ?

I know that up to this point MS don't recommend putting PST files that are in use by Outlook into OneDrive but I thought I'd see if this "All file types" means a change ??


Anyone at MS have a comment ?

8 Replies
best response confirmed by Dorje McKinnon (Steel Contributor)
Yes it will work with pst however it will only sync after the file is unlocked so it would only sync when outlook is closed etc.

From the South Pacific, many thanks @Chris Webb  for responding so quickly.


One Question about Volume transferred:

Use case : As a rural farmer advisor (my users), I have been working for the company 15 years and have a large PST file (3Gb) in my OneDrive. Periodically my laptop falls into a river or gets run over by farm machinery. To make sure I get back everything that I care about when I get a replacement laptop does this mean I need to:

- close outlook every day

- leave my laptop and OneDrive running

- allow for the 3Gb sync to the copy of the PST file in OneDrive online 

- allow for the 20MB of email that came in that day to sync to the copy of the PST file in OneDrive online 



Many thanks Dorje



It’ll sync the changes only during a window before or after outlook is running so 20mb.

I highly recommend moving the pst import to exchange archive if possible.

Syncing PSTs to OneDrive is a recipe for disaster, there are zero good reasons to do so, and a million reason why you should avoid using PSTs altogether. There will be no change in Microsoft's recommendation about PSTs at any time in the future, they're a legacy solution you should avoid using wherever possible.

Hi @Chris Webb  Many thanks for that super quick response when I imagine you're really busy getting ready for ignite.

Hi @Vasil Michev 


Thanks for pointing that out. I totally agree. Our challenge is capacity (IT team and staff) to change those habits as part of our OneDrive roll out.

At this point I don't know how large / small the issue is. But where we can we'll import any PSTs we find into O365 as we go during the OneDrive roll out.

@Dorje McKinnonHi, I wouldn't count on protecting data by backing up PST's... 


If you are using a PST you must be connecting to a pop or imap type of mail server.


You might want to consider upgrading to a mail system like o365 or something similar that will support an OST.

When using outlook with a mail server that support an OST (local cache of your mail) then the mail data is ALWAYS on the server and you never have to worry about the data on your local machine being "lost" or synced or backed using "OneDrive"... etc.  The OST is just for local performance and search indexing.


Another advantage, you can access and change your mail on any device, workstation, web access, mobile phone and all devices will always have the same data since it is the server they are connecting to.

@George P 

what I find interesting is that Outlook will put the pst files on OneDrive if the user decides to backup the Documents folder. Outlook files ist in a folder under Documents and hence will be part of a backup anyway. The user needs to actively move the Outlook Files folder from Documents to another location. Wouldn't it be logical to assume the Windows 10, OneDrive and Office team have done some sort of integration testing .